Networking features in Docker Desktop for Windows

Estimated reading time: 3 minutes

Docker Desktop for Windows provides several networking features to make it easier to use.

Features

VPN Passthrough

Docker Desktop for Windows’s networking can work when attached to a VPN. To do this, Docker Desktop for Windows intercepts traffic from the containers and injects it into Windows as if it originated from the Docker application.

Port Mapping

When you run a container with the -p argument, for example:

$ docker run -p 80:80 -d nginx

Docker Desktop for Windows makes whatever is running on port 80 in the container (in this case, nginx) available on port 80 of localhost. In this example, the host and container ports are the same. What if you need to specify a different host port? If, for example, you already have something running on port 80 of your host machine, you can connect the container to a different port:

$ docker run -p 8000:80 -d nginx

Now, connections to localhost:8000 are sent to port 80 in the container. The syntax for -p is HOST_PORT:CLIENT_PORT.

HTTP/HTTPS Proxy Support

See Proxies.

Known limitations, use cases, and workarounds

Following is a summary of current limitations on the Docker Desktop for Windows networking stack, along with some ideas for workarounds.

There is no docker0 bridge on Windows

Because of the way networking is implemented in Docker Desktop for Windows, you cannot see a docker0 interface on the host. This interface is actually within the virtual machine.

I cannot ping my containers

Docker Desktop for Windows can’t route traffic to Linux containers. However, you can ping the Windows containers.

Per-container IP addressing is not possible

The docker (Linux) bridge network is not reachable from the Windows host. However, it works with Windows containers.

Use cases and workarounds

There are two scenarios that the above limitations affect:

I want to connect from a container to a service on the host

The host has a changing IP address (or none if you have no network access). From 18.03 onwards our recommendation is to connect to the special DNS name host.docker.internal, which resolves to the internal IP address used by the host. This is for development purpose and will not work in a production environment outside of Docker Desktop for Windows.

The gateway is also reachable as gateway.docker.internal.

I want to connect to a container from Windows

Port forwarding works for localhost; --publish, -p, or -P all work. Ports exposed from Linux are forwarded to the host.

Our current recommendation is to publish a port, or to connect from another container. This is what you need to do even on Linux if the container is on an overlay network, not a bridge network, as these are not routed.

The command to run the nginx webserver shown in Getting Started is an example of this.

$ docker run -d -p 80:80 --name webserver nginx

To clarify the syntax, the following two commands both publish container’s port 80 to host’s port 8000:

$ docker run --publish 8000:80 --name webserver nginx

$ docker run -p 8000:80 --name webserver nginx

To publish all ports, use the -P flag. For example, the following command starts a container (in detached mode) and the -P flag publishes all exposed ports of the container to random ports on the host.

$ docker run -d -P --name webserver nginx

See the run command for more details on publish options used with docker run.

windows, networking